A Record Of Environmental And Monsoon Change Between38,000and17,000Calendar Years B.P. Indicated By Diatom Assemblages From Maar Lake Huguangyan

Since Last Glacial Maximum, the globle climate entered a mutation period, appears repeatedly and regular altering cold and warm climate event. This aroused domestic and foreign scholars’s attention and research. From the record of HuLu’s stalagmite, we know the climate event of Last Glacial Maximum, The time of some events can not completely correspond with Greenland GRIP oxygen isotope, is this time error or lag behind between climate events? The only way is to find proxy that could record on behalf of cold events in the same way(such of winter monsoon index) to explain this question, and also could record warm and humid summer monsoon index. Diatoms may be a feasible index.We choose HuGuangyan, in Zhanjing city, Guandong Province as research area, Its climate is chatacterized by:short summer and long winter, full rainfall, and long rainy season; prevailing northwest wind in winter and southeast wind in summer, monsoon climate is obviously. This is iddal area to study monsoon. Huguangyan is a Maar Lake, It’s sediment provide a high-resolution record of paleoenvironmental paleoclimate.Firstly,we establis diatoms as the indicator of the monsoon, we use two main species of diatoms. From different wind power of Alucoseira granulata and Cyclotella stelligera, in order to establish the raio of A.granulata and C.stelligera as proxy of winter monsoon. We use the ratio of planktonic and benthic to reflect changes of lake water levels, changes of the rainfall, as proxy of summer monsoon.We choose C in seven cores as research subject, we use AMS14C method to know16reliable aboulute age, and use linear interpolation to get all the age of samples is between80and38ka B.P.Then handle producer, finally, we identify slide with a microscope. We know some knowledge from analyze.1. We identify HuGuangyan C-hole diatom fossil has28genera and136kinds, planktonic diatom has3genera and5kinds. Mainly for Aulacoseira granulata, Aulacoseira ambigua, Cyclotella pliostelligera and so on. Benthic diatoms has25genera and131kinds, maily for Achnanthes acares, Achnanthes lanceolata, Punctastriata pinnata and so on. 2. We reconstruct changes of38-17ka Maar Lake Huguangyan, form the ratio of planktonic and benthic diatoms, we record lake level experieced stable-rapid rise-slow decline evolutionary history in HuGuanyan area in the time of38-17ka.3.Through the fixed species’relationship of diatoms, we reconstruct winter wind’s phases from prosperity to abate, then to the gentler phases in38-17ka periods. We analyze Hulu cave’s Stalagmite, the Greenland ice core oxygen isotope, Guliya ice core oxygen isotope, the Antarctic ice core methane concentration,this shows that our country the climate in this period is not only subject to global climate, but also has regional climate characteristics.4. We know some things through reconstructing change relationship between winter and summer monsoon:in the times of38-17ka,winter summer monsoon is a shift in the process of change.5.From biodiversity analysis, we use Simpson and Shannon-wiener index on the Last Glacial Maximum during Maar Lake diatom we conduct a conclusion:When diatoms’s living environment becomes complicated, diatom’s species corresponded to rich, Biodibersity index becomes big; Conversely, diatoms’s living enviroment becomes relatively straightforward. Only diatom adapt to the prevailing environmental conditions,genus may reduct, and biodiversity index decreased.